Electrochemical Study of Na2Fe1−xMnxP2O7 (x = 0, 0.25, 0.5, 0.75, 1) as Cathode Material for Rechargeable Na-Ion Batteries

Sodium-ion batteries (SIBs) are considered a good choice for post-lithium devices. Transition metal sodium pyrophosphates are among the most interesting cathode materials for SIBs. Here we study the electrochemical properties of the system Na2Fe1−xMnxP2O7 (x = 0, 0.25, 0.5, 0.75, 1). By means of cyclic voltammetry (CV) and galvanostatic experiments, we confirm that pure Fe and Fe-rich compounds are promising for application in sodium batteries, whereas Mn-rich samples are less satisfactory, at least in case of solid-state reaction recipes and standard slurry preparations. Proper carbon coating is likely needed to improve the electrochemical behavior of Mn-rich samples.